Signaling system for party telephone lines



May 31, 1932. w, EDWARDS 1,860,457

SIGNALING SYSTEM FOR PARTY TELEPHONE LINES v Filed June 15. 1951 aarty J INVENTOR 1 6 C ATTORNEY Patented May 31, .1932

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- NE: lll? EL GM M 1 $I EQ "sreNAmiie SYSTEM roe PARTY g t r mps Application filed June 15, 1931. Serial 1*Io. 5 14,601

stood from the following, description, to;

gether with the accon panying drawings, in r Figures 1 and 2 of: which the ini'zen;

This invention relates to telephone systems and-, more particularly, to improvements in signaling arrangements for subscribers stations on party lines connectedtolsuch systerns.

, Inthe signaling arrangements of the invention, there is-provided at each subscribers station, on thelparty line, a vacuum tube oscillator whose circuits are so arranged that they will be energized entirely by the ringing current comingin over, the line. Subscribers stations with signaling arrangements of this character aredisclosed in a copending application inthe name of EVFH. Edwards, Serial No. 544,605, filed June 15,1931. An audible, responsiyedevice, such as a tele phone receiver, :will' ibe included "in the plate circuit of each oscillator tosignal the subscriber; Alternating signaling current, with direct current oit' either-positive or negative polaritysuperlmposed thereon, wlll be used for signaling purposes whose signaling featureis derived-from the fact that the vacuum tubeused inthe oscillator circuit will not operateunless the positive, side of the plate voltage is connected to the plate. l Of the two parties rung on the same side of the line, the plate otone party'is connected to the line and the plateof the other party is connected to grounch By ringing wit-ha positive or-negative" superimposed current, only one party will be signaled at a'time under such conditions. f

The ringingarrangements of the invention will make it easier to control the pitch and volume of the signal than heretofore and will also give a more pleasing tone than former signaling arrangements. The fact that signaling-arrangements of the invention may be operated solely by the incoming ringing current'will result in reducingthe initial cost of the devices and" lower maintenance thereatter, as the use of relays and ringers or a o powersupply set for the A and Bcurrent 0i an'oscillato'r at eachsubscriber station is eliminated Other obgects and featuresof the invention will" appear more fully from the tion is illustrated; Fig, 1 is a circuit dia;

gram showing the selective signaling a1;

rangements of the invention, a s,applied;to,a

fourf-partyline. InfFigfQare shownc'ures, il ustrating the general manner; in which e-. lectivity obtained.

be connecteda plurality of--. subscribers sets.

inthe jack J As the ringing is accomplished g v by. utilizing alternating current with direct current of either polarity superimposed-thereon, there would be provided;- at the central;

office four keys such as K K ,K and; K Then-the key K is operated; alternating-cue.

rent; from the generator G1 withpositive di; rect current. fronrthe battery B superimi posed thereon, will be;applied.to,tl;1ering side of. thejline L and the tip will; be 1 connected 1 to ground. VlZhenQthekey'K is, operated al-f ternatlngcurrent from the generator G with negative" direct current Ffro'm the battery, B21 superimposed thereon, will bea'ppliedpto the; ring side of the line and; the tip will= hereonnected to ground; lYlien the key-KY5 is operated, alternating current .from the generator G with'pos'itive direct current from the bat-' tery B superimposed thereon, will'be applied to the tip side of the line and the ring side of?" the line will be grounded; When keyK is}:

operated, alternating current from thegenerator G with negative direct current. from the battery B 'superimposed'thereon, will be appliedto the tip side ofi'th'e line and-the v ringside of the line will be. grounded; "Four subscriber stations areishown and connected to the line. These arethe negativeiparty l,

which will be rung by superimposednegative current applied to the tip side of-the line th e'negative party 2, whichwill' be rung when negative superimposed current is applied-to l the ring side of the line the positive party 3, which will be rung when positive superim posed current is appliedto tliefltip 'side of the I line;and the positive'party 4, which will be rung when positive superimposed current is detailed description thereof hereinafter applied to the ring side of the line. At each station, there is provided a vacuum tube oscillator such as the oscillators 5, 6, 7 and 8, which will operate when a certain type of ringing current is applied to one of the lines. Each station will have an audible, responsive device, such as 9, 10, 11 and 12, connected in the plate circuit of the oscillator to give an audible signal to the subscriber.

The operation of the arrangements of the invention is as follows: If it is desired to ring the positive party 3, the key K will be operated, thereby grounding the ring side of the line and connecting positive superimposed current to the tip side of the line. The alternating current will be transmitted through the transformer 15 which is bridged across the line and will furnish a filament current for the tube 7. The plate voltage for the oscillator tube will be obtained from the positive component of the superimposed current consisting of a positive pulse of alternating current from the generator G and positive current from the battery B The filament will be grounded, whereas the plate circuit will be connected. to the tip of the line.

The operation of the oscillator 7 on the positive superimposed ringing current and its non-operation on negative superimposed ringing will be more clearly understood from reference to Fig. 2. An oscillatory vacuum tube circuit has the characteristic that it will oscillate when the applied plate voltage is between certain positive values. During the time the plate is negative, the plate current is zero. Curve A is the characteristic curve for a vacuumtube. The oscillation limits are between the dotted lines X to Y. Curve B illustrates the voltage applied to the plate at party 3 when positive superimposed ringing current is applied to the tip side of the line. It will be seen from Fig. 2 that when the voltage is between the limits X and Y the tube 7 will oscillate and give an audible signal in the receiver 11. When the small negative portion of the voltage from the positive superimposed current is applied to the plate the tube stops operating for the duration of the negative voltage. the "oltage across the plate of tube 7 when negative current is applied to the tip side of the line. \Vhen the large negative voltage is applied to the plate, the tube 7 will not oscillate. WVhen the smaller positive voltage is applied it is below the oscillation limit X and the tube will not oscillate. Thus selectivity between ringing with positive and negative superimposed currents is provided.

.Referring to the negative party 1 on the tip side of the line, the positive superimposed current will not operate the oscillator 5 because the plate of tube 5 is connected to.

ground and the filament is connected to the tip side of the line. Thus the plate of tube 5 is, negative with respect to its filament when Curve B illustrates the plate of tube 7 is positive with respect to its filament. To sound the signal of negative party 1, the key K is operated transmitting negative superimposed ringing current over the tip side of the line. Under such conditions the tube 5 will oscillate.

If it is desired to ring the negative party 2, the key K will be operated. This will ground the tip side of the line and apply negative superimposed current to thering side of the line. The alternating current through the transformer 14 will furnish filament current for the oscillator tube 6. The plate circuit potential is obtained from the superimposed current from the battery B and the generator G The negative side of the battery is connected to the filament terminal of the plate circuit. The plate electrode is connected to ground and hence to the positive side of battery B Accordingly, the positive side of the plate voltage is connected to the plate, and the vacuum tube will oscillate and cause the receiver 10 to give an audible signal to the subscriber. The positive party 4 will not be operated by this application of ringing current, as the plate electrode of the tube 8 is connected to the ring side of the line and hence to the negative side of the plate voltage.

To operate the positive party 4, thekey K, should be operated on positive superimposed current applied to the ring side of the line.

In case it is desired to change the sensitivity of the oscillator tubes to the various ringing voltages this may be done by connectin a C battery in the grid circuits of the tu s in the well known manner.

The arrangements described herein for superimposed ringing current will of course work satisfactorily on pulsating ringing current as well.

While the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of embodiment in many and other widely varied forms without departing from the spirit of the invention, as defined by the appended claims.

\Vhat is claimed is: f

1. A party telephone line signaling system comprising a line, means for applying alternating current with direct current of either polarity superimposed thereon to either the tip or ring side of said line, a plurality Y of subscribers sets connected to said line, vacuum tube oscillators with audible responsive devices in their plate circuits at each of said subscribers sets, means for supplying the filament current for each of said tubes from the alternating current applied to the line, and means forobtaining selectivity in the operation of said oscillations by supplying the plate potential for said tubes from the different signaling current potentials applied to said line.

2; A party telephone line signaling system comprising a line, means for applying alternating current with direct current of either polarity superimposed thereon to either i the tip or ring side of said line, a plurality of subscribers sets connected to said line, vacuum tube oscillators with audible responsive devices in their plate circuits at each of said subscribers sets, means for supplying the filament current for each of saidtubes from the alternating current applied to the line, means for grounding the plate of one of. said tubes and for connecting the fila- V ment thereof to the tip side of the line, means for grounding the plate of another of said tubes and connecting the filament thereof to the ring side of the line, means for grounding the filament of another of said tubes and connecting the plate thereof to the tipside ge of the line, and means for groundingthe filament of another of said tubes and connecting the plate thereof to the ring side of said line. I

3. A party telephone line signaling system comprising a line, means for applying alternating current with direct current of either polarity superimposed thereon to one of the sides of said line, a plurality of subscribers sets associated with said line, vacuum tube oscillators with audible responsive devices in their plate circuits at each of, said subscribers sets, and means for connecting the plate circuits of said oscillators to the side of the line to which said superimposed current is normally applied to signal the subscriber so that the plate of only one ofsaid oscillators will have a positive potential with respect t to its filament for a particular application of I said'superimposedcurrent to said side of the .10 llne.

V 4. A party telephone line signaling system comprising a line, means for applying alternating current with direct current of either polaritysuperimposed thereon toeither side of said line, a plurality of subscribers sets associated with said line, vacuum tube oscillators with audible responsive devices actusated thereby at each of said subscribers sets,

means for supplying the filament current for so each of said tubes from the alternating'current applied to'said line, means for supplying the plate circuit potential for each of said tubes from the superimposed direct and alternating current applied to said line, and means for connecting said tubes to said line, so that for a given application of said current to said line only one of said tubes will have its plate connected to the positive side of a source of plate potential.

ec In testimony whereo I'have Signed my name to this specification this 12th day of June, 1931.

' WILLIAM H. EDWARDS. 

